Incomprehensible output from I2C scanner sketch

Schematic

My aim is to use VL53L0X sensors as proximity detectors. Simultaneous readings below a threshold will trigger a state change response at the device site and a notification via Blynk.
I have had two of these sensors working in the "VL53L0X_dual" example a few days ago but failed since.
In an effort to trace the problem I have run the I2C scanner sketch,
(link immediately below and code pasted below.) Schematic above

With no devices attached to Arduino MKR NB 1500, run I2C Scanner unmodified from ;
https://playground.arduino.cc/Main/sourceblock_1/index.txt?action=sourceblock&num=1
via
https://playground.arduino.cc/Main/I2cScanner/
serial output is;
15:58:45.180 ->
15:58:45.180 -> Scanning...
15:58:45.180 -> I2C device found at address 0x60 !
15:58:45.180 -> I2C device found at address 0x6B !
15:58:45.180 -> done

I then attached sensors to the arduino,
Arduino 5v to sensor Vin, Arduino Gnd to sensor Gnd,
A5 to Sensor SCL and A4 to sensor SDA.

With one VL53L0X TOF sensor device attached to Arduino MKR NB 1500, run I2C Scanner,
Serial output is;
16:06:37.474 ->
16:06:37.474 -> I2C Scanner
16:06:37.474 -> Scanning...
16:06:37.474 -> I2C device found at address 0x60 !
16:06:37.474 -> I2C device found at address 0x6B !
16:06:37.474 -> done

With two VL53L0X sensors (different from the previous run) attached to Arduino MKR NB 1500 in parallel, run the I2C Scanner,
Serial output is;
16:13:58.174 ->
16:13:58.174 -> I2C Scanner
16:13:58.174 -> Scanning...
16:13:58.174 -> I2C device found at address 0x60 !
16:13:58.174 -> I2C device found at address 0x6B !
16:13:58.174 -> done

Thinking there may be something wrong with my MKR-NB-1500 board I repeated these tests with an UNO and
all I got was a single time stamp then testing with 0,1 and 2 sensors respectively.

I am struggling to understand how I get non existent I2C devices showing up on the MKR1500 and nothing on the Uno with the same hardware attached running the same sketch.
Any suggestions for a way forward will be graciously received.
Kind regards
Vere

 // --------------------------------------
// i2c_scanner
//
// Version 1
//    This program (or code that looks like it)
//    can be found in many places.
//    For example on the Arduino.cc forum.
//    The original author is not know.
// Version 2, Juni 2012, Using Arduino 1.0.1
//     Adapted to be as simple as possible by Arduino.cc user Krodal
// Version 3, Feb 26  2013
//    V3 by louarnold
// Version 4, March 3, 2013, Using Arduino 1.0.3
//    by Arduino.cc user Krodal.
//    Changes by louarnold removed.
//    Scanning addresses changed from 0...127 to 1...119,
//    according to the i2c scanner by Nick Gammon
//    https://www.gammon.com.au/forum/?id=10896
// Version 5, March 28, 2013
//    As version 4, but address scans now to 127.
//    A sensor seems to use address 120.
// Version 6, November 27, 2015.
//    Added waiting for the Leonardo serial communication.
// 
//
// This sketch tests the standard 7-bit addresses
// Devices with higher bit address might not be seen properly.
//

#include <Wire.h>


void setup()
{
  Wire.begin();

  Serial.begin(9600);
  while (!Serial);             // Leonardo: wait for serial monitor
  Serial.println("\nI2C Scanner");
}


void loop()
{
  byte error, address;
  int nDevices;

  Serial.println("Scanning...");

  nDevices = 0;
  for(address = 1; address < 127; address++ ) 
  {
    // The i2c_scanner uses the return value of
    // the Write.endTransmisstion to see if
    // a device did acknowledge to the address.
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0)
    {
      Serial.print("I2C device found at address 0x");
      if (address<16) 
        Serial.print("0");
      Serial.print(address,HEX);
      Serial.println("  !");

      nDevices++;
    }
    else if (error==4) 
    {
      Serial.print("Unknown error at address 0x");
      if (address<16) 
        Serial.print("0");
      Serial.println(address,HEX);
    }    
  }
  if (nDevices == 0)
    Serial.println("No I2C devices found\n");
  else
    Serial.println("done\n");

  delay(5000);           // wait 5 seconds for next scan
}

I am struggling to understand how I get non existent I2C devices showing up on the MKR1500 and nothing on the Uno

Does the board have any built in devices such as an SD card slot that might be using I2C ?

That board has an ECC508 AUTH chip connected to the I2C bus. Perhaps this is what you are seeing?

1 Like

The radio has an I2C interface.

1 Like

Since posting I have checked the ADC function of pins A4 and A5 by running the Arduino example sketch; arduino>examples>basic>AnalogReadSerial
and changing the code and attachment of a potentiometer to A4 and A5. Both pins gave the expected serial output which responded as expected to turning the potentiometer.
That suggests to me that I haven't accidentally fried these analog pins, but maybe there is some more subtle damage done?
Any ideas?

Perhaps you damaged the VL53L0X sensors. Post a link to the product page for the modules you have.

It is not entirely clear from your posts what you have done, so try each of them alone on the Uno, with the I2C scanner.

Thank you for your responses,

UKHeliBob, No SD card slot on this board.

missdrew and jremington, the radio and the authentication chip will
be the two I wasn't expecting,
so My board is presumably OK but I may
have done something unfortunate to the sensors. I will check them all individually.
Thanks again for the help.
Vere